Adler et al. (1998) assert there are two possible mechanisms
for the transient effect of nicotine on sensory gating
desensitization of the nicotinic cholinergic receptors or
rapid metabolism of nicotine. If the latter were responsible
for the decrease in effectiveness over time, then repeated
administration, as exhibited in the smoking patterns of
schizophrenics, would counteract the effect of rapid metabolism
and produce longer lasting improvement. However,
despite repetitive smoking, the effect of nicotine appears
to diminish, a pattern that suggests that desensitization
occurs. The authors confirm that the most rapid desensitization
rates in the nicotinic receptor family are α7-nicotinic
receptors, which have been identified as responsible for the
auditory sensory gating deficit in schizophrenics.